Number 3 is not a sin. Participating each week and Holy Day at mass is an obligation that has limitations to your ability to fulfill. If you are ill, you are not obliged. If you are confined, you are not obliged. If you can only get there on foot and it is many miles, you are not obliged.
Number 1 is a sin, but it can vary how serious it is. In my situation, it would be grave. By grave I mean it has the potential to be a mortal sin for me, to have the potential to indicate serious harm in my relationship with God. For a sin to be mortal, it first needs to be grave matter, and then it must furthermore meet other conditions still. Number 2 and number 4 also have the potential to be mortal sins.
With number 4, though, especially, it would be important to look at what is going on with the person. Do they have a relationship with God? What’s going on in their life? Do they live in a remote area with no regular priest (like your number 3)? Maybe they have not done a mortal sin in the last while, and that is why they are not going. Or, maybe they are refusing the sacrament because they think the Church is wrong about confession. Before number 4 can even begin to be a mortal sin, they have to be under a jurisdiction that requires confession (your average Catholic is). A catechumen, for example, is not required to go to confession. They aren’t baptized yet.